The first act is a retelling of what happened in New York in 1965 when a automated switch at a power station started a cascade failure that resulted in a blackout that affected the entire northeast of the United States. The story of how people coped with the chaos is a contrast of the human spirit against the bizarre helplessness our civilization seems to have because of the dependence we have on technology.
The second act is something of a debunking of the romantic notions some people put forth when presented with the notion of everything failing and the prospect of living without technology, in the event of a catastophic systemic collapse.
The third act is about the climactic catastrophy, that happened many centuries ago, that drove mankind from being nomadic wanderer tribes to settling in river valleys as the first nations. We see the changes that needed to happen to bring about civilization. Finally we jump forward in time once more.
A lot of this program is both chilling and strangely prophetic--especially when you take into account what happened in the Nineties, in 2001, and after.

With regard to all that James Burke has done: Should be required study at every High School.

This series strongly influenced me as a teenager, and I have continued to seek it out over the years. Glad to see it is still available on this site.